Re: [Qemu-devel] [qemu-s390x] [RFC 10/15] s390-bios: Support for running format-0/1 channel programs

[Cornelia Huck]

On Fri, 6 Jul 2018 15:03:49 +0200
Halil Pasic <address@hidden> wrote:

> On 07/06/2018 02:26 PM, Cornelia Huck wrote:
> > On Fri, 6 Jul 2018 13:42:25 +0200
> > Halil Pasic <address@hidden> wrote:
> >   
> >> On 07/06/2018 10:03 AM, Cornelia Huck wrote:  
> >>> On Thu,  5 Jul 2018 13:25:38 -0400
> >>> "Jason J. Herne" <address@hidden> wrote:  
> >>>> +    rc = ssch(schid, &orb);
> >>>> +    if (rc) {
> >>>> +        print_int("ssch failed with rc=", rc);

One nit: make this 'cc' instead of 'rc'?

> >>>> +        return rc;  
> >>>
> >>> Are you doing anything like retrying on cc 1/2? It's probably fine to
> >>> give up on cc 3.
> >>>      
> >>
> >> We are in IPL context. We should have exclusive access to the DASD
> >> we are IPL-ing from, or not? My understanding was that if the layers
> >> below us don't violate the rules, we should never observe cc 1 or 2
> >> here. Or am I wrong?  
> > 
> > cc 2 probably not (nobody should be doing a halt or a clear), but cc 1
> > if there's some unsolicited status pending?
> >   
> 
> AFAIK we are supposed to give up then. The status was supposed to be
> cleared away on the reset which precedes IPL. If the device presented
> an unsolicited status between reset and starting the IPL IO on the
> channel I think the IPL should fail.

I very dimly remember efforts to make (non-QEMU) IPL more robust, but I
think that was more about IFCCs and the like.

Anyway, it is probably not worth spending too much time on. Being able
to IPL from vfio-ccw handled dasd is already very nice :)